I agree that you should file a lawsuit if you’re waiting more than 15 months. I waited for 25 months to file it.Your welcome . I believe we need to be patient but active . I would try all possible options to get an answer if none of them work then certainly the only option would to file a lawsuit(written Mandamus )to move your case forward if money is not issue for you . This would be a good idea if somone is waiting for more than a year . This is just my personal opinion not an advise.
USCIS received my I-485 in Oct 2020. I filed the mandamus in Nov 2022 after numerous steps trying to get an answer from them. I did all kind of calling, writing, writing to the White House, contacting congressman, senator, etc but my case was still pending. I’m waiting for the decision from my lawsuit. Hopefully I will get the decision in the next few weeks.
If you file your case in late 2022 and 2023, you will be processed faster because USCIS is trying to make the numbers look nice to the public. They never process “in order receive” like they state on their website. Poor us - applicants from 2020. Our applications are collecting dust in a basement somewhere in NBC that they never touch